This invention relates to a method for automatic analysis of electron beam diffraction pattern in a transmission electron microscope.
A transmission electron microscope capable of displaying electron beam diffraction pattern is very useful for investigation of a crystalline specimen. An electron beam diffraction pattern contains information on the crystal structure of the specimen, its orientation and many others. Analysis of the diffraction pattern, therefore, makes it possible to precisely analyze the crystal structure of the specimen, to identify the specimen materials, and to determine the orientations. The conventional analysis procedures for electron beam diffraction patterns are carried out as follows. First, the diffraction pattern displayed on the diffraction pattern forming plane or on the screen of a cathrode-ray tube (CRT) is photographed on a film, and the film is developed in a darkroom. Then, the position of each diffraction spot or radius of each ring in the diffraction pattern on the developed negative film is measured so as to calculate the d-values (i.e., lattice spacing) of the crystal. The calculated d-values are collated with the many cards (or a data table) recording the d-values corresponding to the various materials, so as to select the one card which closely coincides with the obtained set of d-values of the unknown crystalline material. As a result, the specimen material is identified, and orientation of the crystalline specimen is decided. These analysis procedures, however, required troublesome manual operation such as photographic processing in a darkroom. In addition, specialized knowledge about analysis of crystal structure is required.